A color filter is an essential component to a solid-state imaging device or a liquid crystal display. In a conventional fabricating method, a color filter is produced by forming red, green and blue pixels on a substrate via staining, printing, electro-deposition, pigment dispersing, and etc., wherein the pigment dispersing method is the most common way. The pigment dispersing method is firstly to coat the substrate with a resin composition containing pigments, then expose the substrate covered by a mask, and develop after exposing, and consequently the pixels are formed.
Main ingredients of a resin composition used in a conventional pigment dispersing process includes a alkali soluble resin, polymeric monomers, a photoinitiator, pigments, and solvents, wherein a major component of the alkali soluble resin is monomers at least having a hydroxyl group or a carboxylic acid. Chemical structure, acid value, and molecular weight of the monomer have huge impact on the property of the resin composition and desired pattern formed on a substrate. Different resins used in the conventional manufacturing process are, for instance, carboxylic acid resin, alcohol compound resin, acrylic resin, acrylic-epoxy resin, acrylic-styrene resin, phenol-novolak resin. Although performances of a conventional light transmittable resin composition may be sufficient on resolution, adhesiveness, or developing result under visible light, its performances under infrared ray are not sufficient with respects to transmittance, pattern resolution, adhesiveness and developing result. A conventional light transmittable resin composition cannot have high transmittance under infrared ray and low transmittance under visible light at the same time.
In recent years, color filters of a near-infrared-ray-sensing solid-state imaging device are required to be very thin (for example, it is better to be 1 μm in thickness). However, a conventional infrared ray transmitting filter has high transmittance under visible light due to low thickness, and thus sensing accuracy of the near-infrared-ray-sensing solid-state imaging device is low because of interference from visible light. Moreover, the problem of low sensing accuracy is worse with higher degree of miniaturization of pixels. Therefore, the conventional method meets a difficulty to produce a color filter with a resolution lower than 1.1 μm in a near-infrared-ray-sensing solid-state imaging device.